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Internet X.509 Public Key Infrastructure: Additional Algorithm Identifiers for RSASSA-PSS and ECDSA using SHAKEs as Hash FunctionsCisco Systemspkampana@cisco.comNIST100 Bureau Drive, Stop 8930GaithersburgMD20899-8930USAquynh.dang@nist.gov
General
LAMPS WGDigital signatures are used to sign messages, X.509
certificates and CRLs (Certificate Revocation Lists). This
document describes the conventions for using the SHAKE family of
hash functions in the Internet X.509 as one-way hash functions
with the RSA Probabilistic Signature Scheme and ECDSA signature
algorithms. The conventions for the associated subject public
keys are also described.[ EDNOTE: Remove this section before publication. ]draft-ietf-lamps-pkix-shake-03:
Updates based on suggestions and clarifications by Jim. Added ASN.1.draft-ietf-lamps-pkix-shake-02:
Significant reorganization of the sections to simplify the introduction, the new OIDs and their use in PKIX.Added new OIDs for RSASSA-PSS that hardcode hash, salt and MGF, according the WG consensus.Updated Public Key section to use the new RSASSA-PSS OIDs and clarify the algorithm identifier usage.Removed the no longer used SHAKE OIDs from section 3.1.Consolidated subsection for message digest algorithms.Text fixes.draft-ietf-lamps-pkix-shake-01:
Changed titles and section names.Removed DSA after WG discussions.Updated shake OID names and parameters, added MGF1 section.Updated RSASSA-PSS section.Added Public key algorithm OIDs.Populated Introduction and IANA sections.draft-ietf-lamps-pkix-shake-00:
Initial versionThis document describes several cryptographic algorithm identifiers
for several cryptographic algorithms which use variable length output
SHAKE functions introduced in which can be used
with the Internet X.509 Certificate and CRL profile . The SHA-3 family of one-way hash functions is specified in .
In the SHA-3 family, two extendable-output functions (SHAKEs):
SHAKE128 and SHAKE256, are defined. Four other hash function instances, SHA3-224, SHA3-256,
SHA3-384, and SHA3-512 are also defined but are out of scope for this document.
A SHAKE is a variable length hash function. The output length, in bits, of a SHAKE
is defined by the d parameter. The corresponding collision and second
preimage resistance strengths for SHAKE128 are min(d/2,128) and min(d,128) bits respectively.
And, the corresponding collision and second preimage resistance strengths for SHAKE256
are min(d/2,256) and min(d,256) bits respectively.A SHAKE can be used as the message digest function (to hash the message to be signed)
in RSASSA-PSS and ECDSA and as the hash in the mask generating function in RSASSA-PSS.
In , we define four new OIDs for RSASSA-PSS and ECDSA when SHAKE128 and
SHAKE256 are used. The same algorithm identifiers are used for identifying a public key,
and identifying a signature. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in .The new identifiers for RSASSA-PSS signatures using SHAKEs are below.The new algorithm identifiers of ECDSA signatures using SHAKEs are below.The parameters for these four identifiers above MUST be absent. That is,
the identifier SHALL be a SEQUENCE of one component, the OID. and specify the required output length
for each use of SHAKE128 or SHAKE256 in RSASSA-PSS and ECDSA. In summary, when hashing messages
to be signed, output lengths of SHAKE128 and SHAKE256 are 256 and 512 bits respectively.
When the SHAKEs are used as mask generation functions, their output lengths are (n - 264) or (n - 520) bits
respectively, where n is a RSA modulus size in bits.Signatures can be placed in a number of different ASN.1 structures.
The top level structure for an X.509 certificate, to illustrate
how signatures are frequently encoded with an algorithm identifier
and a location for the signature, is The identifiers defined in can be used
as the AlgorithmIdentifier in the signatureAlgorithm field in the sequence
Certificate and the signature field in the sequence tbsCertificate in X.509
.Conforming CA implementations MUST specify the algorithms
explicitly by using the OIDs specified in when
encoding RSASSA-PSS and ECDSA with SHAKE signatures
in certificates and CRLs. Encoding rules for RSASSA-PSS and ECDSA
signature values are specified in and
respectively.Conforming client implementations that process RSASSA-PSS and ECDSA
with SHAKE signatures when processing certificates and CRLs
MUST recognize the corresponding OIDs.The RSASSA-PSS algorithm is defined in .
When id-RSASSA-PSS-SHAKE128 or id-RSASSA-PSS-SHAKE256 specified in
is used, the encoding MUST omit the parameters field. That is,
the AlgorithmIdentifier SHALL be a SEQUENCE of one component,
id-RSASSA-PSS-SHAKE128 or id-RSASSA-PSS-SHAKE256. The hash algorithm to hash a message being signed and the hash algorithm as the
mask generation function "MGF(H, emLen - hLen - 1)" used
in RSASSA-PSS MUST be the same, SHAKE128 or SHAKE256 respectively. The
output-length of the hash algorithm which hashes the message SHALL be 32 or
64 bytes respectively. In RSASSA-PSS, a mask generation function takes an octet string of variable length and
a desired output length as input, and outputs an octet
string of the desired length. In RSASSA-PSS with SHAKES, the SHAKEs MUST be
used natively as the MGF function, instead of the MGF1 algorithm that uses
the hash function in multiple iterations as specified in Section B.2.1 of
. In other words, the MGF is defined as
and
respectively for id-RSASSA-PSS-SHAKE128 and id-RSASSA-PSS-SHAKE256. The mgfSeed is
the seed from which mask is generated, an octet string. The maskLen for SHAKE128 or SHAKE256 being used
as the MGF is (n - 264)/8 or (n - 520)/8 bytes respectively, where n is the RSA modulus
in bits. For example, when RSA modulus n is 2048, the output length of SHAKE128 or
SHAKE256 as the MGF will be 223 or 191 when id-RSASSA-PSS-SHAKE128 or
id-RSASSA-PSS-SHAKE256 is used respectively. The RSASSA-PSS saltLength MUST be 32
or 64 bytes respectively. Finally, the trailerField MUST be 1, which represents
the trailer field with hexadecimal value 0xBC .The Elliptic Curve Digital Signature Algorithm (ECDSA) is defined in
. When the id-ecdsa-with-SHAKE128 or id-ecdsa-with-SHAKE256
(specified in ) algorithm identifier appears, the respective SHAKE
function (SHAKE128 or SHAKE256) is used as the hash.
The encoding MUST omit the parameters field. That is, the AlgorithmIdentifier
SHALL be a SEQUENCE of one component, the OID id-ecdsa-with-SHAKE128 or
id-ecdsa-with-SHAKE256.For simplicity and compliance with the ECDSA standard specification,
the output size of the hash function must be explicitly determined. The
output size, d, for SHAKE128 or SHAKE256 used in ECDSA MUST be 256 or 512
bits respectively. Conforming CA implementations that generate ECDSA with SHAKE signatures
in certificates or CRLs MUST generate such signatures with a deterministicly
generated, non-random k in accordance
with all the requirements specified in .
They MAY also generate such signatures
in accordance with all other recommendations in or
if they have a stated policy that requires
conformance to these standards. These standards may have not specified
SHAKE128 and SHAKE256 as hash algorithm options. However, SHAKE128 and
SHAKE256 with output length being 32 and 64 octets respectively are
subtitutions for 256 and 512-bit output hash algorithms such as SHA256
and SHA512 used in the standards.In Section 3.2 "Generation of k" of , HMAC is used to derive
the deterministic k. Conforming implementations that generate deterministic
ECDSA with SHAKE signatures in X.509 MUST use KMAC with SHAKE128 or KMAC with
SHAKE256 as specfied in when SHAKE128 or SHAKE256 is
used as the message hashing algorithm, respectively. In this situation, KMAC with
SHAKE128 and KMAC with SHAKE256 have 256-bit and 512-bit outputs respectively,
and the optional customization bit string S is an empty string.Certificates conforming to can convey a
public key for any public key algorithm. The certificate indicates
the algorithm through an algorithm identifier. This algorithm
identifier is an OID and optionally associated parameters.In the X.509 certificate, the subjectPublicKeyInfo field has the
SubjectPublicKeyInfo type, which has the following ASN.1 syntax: The fields in SubjectPublicKeyInfo have the following meanings:
algorithm is the algorithm identifier and parameters for the
public key.subjectPublicKey contains the byte stream of the public key. The
algorithms defined in this document always encode the public key
as an exact multiple of 8-bits.Conforming CA implementations MUST specify the algorithms
explicitly by using the OIDs specified in
when encoding RSASSA-PSS and ECDSA with SHAKE public keys
in certificates and CRLs.
The conventions for RSASSA-PSS and ECDSA public keys
algorithm identifiers are as specified in ,
and
,
but we include them below for convenience.
defines the following OID for RSA AlgorithmIdentifier
in the SubjectPublicKeyInfo with NULL parameters.Additionally, when the RSA private key owner wishes to limit the use of
the public key exclusively to RSASSA-PSS, the AlgorithmIdentifiers for
RSASSA-PSS defined in can be used as the algorithm
field in the SubjectPublicKeyInfo sequence . The
identifier parameters, as explained in section , MUST be
absent. Regardless of what public key algorithm identifier is used, the RSA public
key, which is composed of a modulus and a public exponent, MUST be encoded
using the RSAPublicKey type . The output of this
encoding is carried in the certificate subjectPublicKey. For ECDSA, the public key identifier defined in is
Additionally, the mandatory EC SubjectPublicKey is defined in Section 2.1.1
and its syntax is in Section 2.2 of . We also include them
here for convenience: The id-ecPublicKey parameters MUST be present and are defined as The ECParameters associated with the ECDSA public key in the signer's
certificate SHALL apply to the verification of the signature.[ EDNOTE: Update here only if there are OID allocations by IANA. ]
This document has no IANA actions. The SHAKEs are deterministic functions. Like any other deterministic functions,
executing each function with the same input multiple times will produce the
same output. Therefore, users should not expect unrelated outputs (with the
same or different output lengths) from excuting a SHAKE function with the
same input multiple times.The shorter one of any 2 outputs produced from a
SHAKE with the same input is a prefix of the longer one. It is a similar
situation as truncating a 512-bit output of SHA-512 by taking its 256 left-most
bits. These 256 left-most bits are a prefix of the 512-bit output.Implementations must protect the signer's private key. Compromise of
the signer's private key permits masquerade.Implementations must randomly generate one-time values, such as the k value when generating a ECDSA
signature. In addition, the generation of public/private key pairs
relies on random numbers. The use of inadequate pseudo-random
number generators (PRNGs) to generate such cryptographic values can
result in little or no security. The generation of quality random
numbers is difficult. offers important guidance
in this area, and series provide acceptable
PRNGs.Implementers should be aware that cryptographic algorithms may
become weaker with time. As new cryptanalysis techniques are developed
and computing power increases, the work factor or time required to break a
particular cryptographic algorithm may decrease. Therefore, cryptographic
algorithm implementations should be modular allowing new algorithms
to be readily inserted. That is, implementers should be prepared to
regularly update the set of algorithms in their implementations.We would like to thank Sean Turner and Jim Schaad for his valuable contributions to this document.
&RFC2119;
&RFC4055;
&RFC5280;
&RFC5480;
&RFC8017;
SHA-3 Standard - Permutation-Based Hash and Extendable-Output Functions FIPS PUB 202National Institute of Standards and Technology
&RFC3279;
&RFC4086;
&RFC6979;
SEC 1: Elliptic Curve CryptographyStandards for Efficient Cryptography GroupX9.62-2005 Public Key Cryptography for the Financial Services Industry: The Elliptic Curve Digital Signature Standard (ECDSA)American National Standard for Financial Services (ANSI)Recommendation for Random Number Generation Using Deterministic Random Bit Generators. NIST SP 800-90ANational Institute of Standards and TechnologySHA-3 Derived Functions: cSHAKE, KMAC, TupleHash and ParallelHash. NIST SP 800-185National Institute of Standards and TechnologyThis appendix includes the ASN.1 modules for SHAKEs in X.509.
This module does not come from any existing RFC.